Plastic draw press



April 18, 1961 R. F. TABER 2,979,771

PLASTIC DRAW PRESS Filed Sept. 30, 1957 3 Sheets-Sheet 1 INVENTOR United States PatentG PLASTIC DRAW PRESS Ralph F. Taber, 111 Goundry St., North Tonawanda, N.Y.

Filed Sept. 30, 1957, Ser. No. 687,261

Claims. (Cl. 18;-19)

This invention relates to improvements inpresses, particularly to presses for drawing plastic sheet material.

The invention provides a draw press for drawing plastic box covers in which a sheet of plastic material is retained against a stationary drawing die by a movable die normally moved toward and held against the stationary die by substantially uniform fluid pressure while a punch draws the material in cooperation with the stationary die. The punch is formed to engage and move the movable die away from the stationary die when the forming operation is completed. The means operating the punch provides suflicient force to move the movable dle away from the stationary die against the fluid pressure. The fluid pressure means is formed to contain a suflicient volume of fluid under pressure so that movement of the movable die between operative and inoperative positions relative to the stationary die does not make any appreciable change in pressure. The fluid pressure means retains fluid under pressure for flow back and forth to a cylinder having a piston for operating the movable die without loss of fluid in normal operation.

The invention provides more economical operation of a draw press by fluid pressure because fluid exhaust each time the movable die is operated eliminated, while substantially uniform fluid pressure operation of the movable die secures a better result in uniformly holding sheets to be formed against the stationary die. The exhaust fluid from the operating cylinder in moving the punch is used to cool the punch, eject the formed pieces and the pieces of the blank left after the forming operation from the press. 7

The invention provides a draw press having the combination of a pair of coaxially arranged cylinders and pistons therein, one of the pistons operating the punch and the other operating the movable die for cooperation with a stationary forming die in forming plastic sheet material. The pistons support the punch and movable die so the movable die engages and holds a sheet to be formed before the sheet is engaged by the punch. The punch is arranged to engage the movable die at the end of a forming operation and move it away from the stationary die against fluid pressure normally moving the piston connected to the movable die toward the stationary die.

The invention provides a draw press construction having a punch cylinder in end to end relation to the movable die cylinder. The movable die cylinder is arranged in concentric relation about the punch piston rod and has a cylindrical piston for operating the movable die. Acylindrical extension on the cylindrical piston carries the movable die adjacent the punch. The movable die is of ring shape and extends about the punch beyond the end of the movable die cylinder for cooperative movement toward and from the stationary forming die.

der for normally operating the movable die piston to movethe movable die toward the-stationary die. Manually controlled :means connects a source of fluid under A fluid, pressure container is connected to the movable die cylin- "ice , movable die.

A cushion mechanism is provided for controlling the speed of operation of the punch piston as it engages and'forms the sheet. This provides means for timing" the-movement of the punch so plastic sheets may beefliciently drawn without likelihood of being damaged."-

In the drawings:

Fig. 1 shows'a fragmentary front elevation of a'press with portions broken away and shown in cross section; for illustrating the details of construction.

Fig. 2 be horizontal cross section taken on line 2-2' of Fig. 1.'

Fig. 3 is a detail vertical cross-section taken on line 3-3 of Fig. 1.

Fig. 4 is a diagrammatic view showing the pipe connections, valves and other parts used in connecting the variousparts of the press for fluid pressure'operation.

Fig. 5 is a diagrammatic view showing an arrangement of the passages in the main pressure control valve for controlling operation of the press.

A draw press made according to the invention has a base indicated at 1 provided with a top 2, a portion of which is illustrated in Figs. 1 and 2. The central portion of the top on the base is formed with an opening 3 through which formed parts are ejected. A lower die holder 4 is mouned on the upper face of top 2 and has a central opening in registry with opening 3. The upper face of lower stationary die holder 4 is recessed to re-- ceive lower or stationary die adapter 5. Lower die holder 7 4 has an annular groove 6 formed therein opening up wardly through the recess in the upper face for receiving an electric heating element. The lower die adapter 5 is formed with a central opening in registry with opening 3 which is slightly smaller in size. The upper face of adapter 5 detachably mounts the lower or stationarydrawing or forming die member 7. The lower face of stationary forming die 7 sets on the upper face of adapter 5 and the die is formed with a central opening having the desired size and shape for receiving and forming sheet material therein. The upper edge of stationary forming die 7 has a forming projection 8 extending inwardlyinto the opening therein for cooperation in drawing sheet" material and with the upper edge formed for cutting the edge portion of a formed piece of sheet material in cooperation with a trimmer associated with a drawing punch. The stationary forming die 7, adapter 5 and lower die holder 4 are all detachably secured to each other and to the top of the base.

A pair of posts 9 have the lower ends rigidly bolted: to top 2 and base 1, extend upwardly in spaced parallel relation and carry a supporting frame or crosshead casting 10 rigidly bolted to the upper ends. Supporting frame 10 extends over the base and top in substantially horizontal relation above stationary forming die 7. Frame 10 is shown as being formed of a casting having top and bottom walls, front and back side walls and closed ends connecting the end portions of the several. walls. This frame is of rectangular shape in cross sec-.= tion. Frame 10 is formed with a movable die cylinder- 11 extending from the top to the bottom walls in aligned relation with the axis of stationary forming die 7, asshown in Figs. 1 and 3. A piston guide 12 is mounted on the lower wall of frame It} in coaxial relation with cylinder 11.

The press as shown in Fig. 1 has frame 10 and;the supported parts moved toward the base with the movable;- die and punch not spaced the full distance-abovestw,

The pressure for operating the punch is suflicient I ment.

tionary die when positioned at the upper limit of move- This facilitates illustration of the parts on a larger scale.

A punch cylinder is mounted in upwardly extendingrelation on the top wall of framemember 10. Punch cylinder 15 has a cylinder base 16 formed with a 'projection 17 on the lower end engaging in a complementary recess-formed in the top wall of member 10, as shown in Figs. 1 and 3. A cylinder shell 18 has the lower end detachably mounted on base 16. "A cylinder cap 19 is mounted on the opposite or upper end of punch cylinder shell 18. Both punch cylinder base 16 and cap 19 are formed with fluid passages having pipe connections communicating therewith for supply and exhaust of fluid under pressure to opposite ends of the punch cylinder 15 in a manner hereinafter described. A punch piston 20-is slidably mounted in'punch cylinder 15 for reciprocating movement between the'base and cap in shell 18. A piston rod 21 has one end secured to piston 20 with an enlarged cylindrical portion 22 adjacent piston 20 providing rounded lower end and shoulder 23 adapted to slidably engage in cushion chamber 24 when the' piston is approachingthe lower portion of its movement in the cylinder where the forming operation begins. Piston rod 21 extending from shoulder 23 slidably engages in cylinder base 16 and extends downwardly through movable die cylinder 11 in axial relation. The lower end of piston rod 21 extends through piston guide 12 toward the base and has a reduced extension 25 formed with a passage 26. Extension 25 has the lower end threaded internally in passage 26. Passage 26 has an outwardly extending portion at the upper end opening through the surface just below shoulder 27 formed on the piston rod at the upper end of reduced extension 25.

-A cylinder head plate 28 is detachably secured in a recess at the upper end of movable die cylinder 11 in the top wall of frame 10. The recess receiving cylinder head plate 28 opens into the recess receiving projection 17 on cylinder base 16 so that head plate 28 is below cylinder base 16, as shown in Figs. 1 and 3. Cylinder head plate 28 has a central opening slidably receiving piston rod 21. A packing gland 29 is mounted on the lower or inner face of cylinder head plate 28 for sealing the upper endrofthe movable die cylinder against leakage of fluid about piston rod 21 and head plate 28.

A cylindrical or movable die piston 30 is mounted for reciprocation in movable die cylinder 11 about piston rod 21 and has a packing gland 31 on the top face for sealing cylinder 11 about the piston rod to retain fluid under pressure in the upper end of cylinder 11. Cylindrical piston 30 has a cylindrical extension or piston rod 32- projecting downwardly through the lower end of cylinder 11, slidably guided in piston guide 12 and having an annular supporting flange 33 on the lower outer end beyond piston guide 12. Piston rod 21 slidably extends through flange 33. An upper or movable die holder 34 has a plate portion 35 bolted or otherwise detachably secured to flange 33 of the movable die piston structure. A leather or other suitable type washer 36 is engaged betweenplate portion 35 and annular supporting flange 33 for reducing shock transmission in the operation of the press. Upper movable die holder 34 has the periphery of plate portion 35 formed with a plurality of arcuate arms 37 extending downwardly and toward the stationary die member. The free ends of arms 37 are formed with radial outwardly extending attaching feet 38. An upper or movable die holder plate 39 of ring shape has a pair of spacing washers 40 and 41 engaged between the upper face thereof and the lower faces of attaching feet 38. Suitable bolts or attaching means rigidly secure die holder plate 39 to movable die holder 34 by engaging feet 38 and plate 39.

The lower face of movable die holder plate 39 has a seat formed on the inner portion to receive movable die adapter 42 and an annular groove in the outer portion to receive die heater element 43 therein. Adapter 42 is secured to holder plate 39 by bolts extending through the plate with the lower endsthreaded in the adapter. The heads of the bolts engage the upper surface of the plate 39 and are received in apertures formed in spacing washers 40 and 41. Movable or drawing die 44 is detachably bolted or otherwise rigidly secured to movable die adapter 42, as shown in Fig. 1.. Movable drawing 7 engaging the lower end of piston guide 12.

die 44 is of ring shape and has substantially the same size as stationary drawing or forming 'die 7. The lower face of movable die 44 is flat and adapted to be moved toward and from stationary die-.7 for engaging and holding a piece of sheet material to be formed or drawn with her having a size to fit within arcuate arms 37, as shown in Fig. 1. Punch holder 50 has a tubular central portion 51 slidably fitting reduced extension 25 on the piston rod with thevupper end seated against shoulder 27. A tubular boss- 52 is formed on the upper end of punch a i holder 50 for receiving the lower end of piston rod 21 movable die holder in upward movement to limit relaabove shoulder 27 and carrying suitable means, such as a set screw, for, securing the punch holder to the piston rod. The upper end of boss 52 engages a leather washer I 53 mounted on the under side of plate portion 35' of the tive movement of the punch holder to the upper movable die holder' for movement together to their upper limit. Punch holder has chamber 54 for receivingcooling fluid through a pipe fitting 55 while an exhaust opening 56 is provided in the outer side thereof. The

lower end of punch holder 50 extends below the: end of extension 25 on the piston rod and has a flat face receiving trimmer 57 in abutting relation. Punch 58 has the upper face abutting the lower face of trimmer 57 and a shank of the same size as piston rod extension 25 'projectiug through an opening in the trimmer and engaging in thelower end of tubular central portion 51 of punch holder 50. An attaching screw 59 has the head engaging in a recess in punch 58 and the body extend- .ing through a passage in the shank on the punch and threaded in the threaded passage 26 in the lower end of piston rod extension 25. Screw 59 has a central passage forrned therein communicating with the passage 26 formed in extension 25 to exhaust fluid under pressure Y downwardly and outwardly from the lower end 'of punch 50 for ejecting a formed sheet portion downwardly from the punch through the openings in the dies and through opening 3 in top 2. The outer end'of passage 26 communicates with an annular groove formed in tubular cen- 'tral portion 51. A radial passage 48 extends from the annular groove to the outer surface of holder 50 where a'pipe fitting 49 is secured to punch holder 50 in communication with passage 48 to supply fluid under pressure thereto from a suitable source as hereinafter described 7 It is necessary to control the speed of movement of the punch from the time it engages the sheet to be formed until the forming or drawing operation is completed. For this purpose, piston rod 21 has enlarged portion 22 formed on the upper end, move into cushion chamber 24 formed in cylinder base 16 when punch 58 is about to engage the sheet to be formed. Packing gland 60, Fig. 3, engages enlarged portion 22 as it enters cushion chamber 24 where the fluid in chamber 24 is compressed immediately to resist movement of the piston rod and punch. A fluid passage 61 extends radially outward and has an upward extension 62 opening into the punch 6 cylinder. A cushion adjusting screw 63 is threaded in cylinder base 16 in the outer end of fluid passage 61 and has the inner end controlling the passage of fluid from cushion chamber 24 through passage 61 into upward extension 62. Cushion screw 63 is manually operable to control the flow of fluid in passage 61 and thereby control the speed of movement of the punch during the downward movement through movable and stationary dies 44 and 7 in forming a piece of sheet material.

The movable die holder 34 is formed with a projection 64 extending outwardly from plate portion 35, as shown in Fig. 1. Projection 64 has a threaded opening having the lower end of switch operating rod 65 threaded therein and retained in adjusted position by lock nut 66. The lower terminal portion of operating rod 65 slidably engages in the bifurcated end portion of guide plate 67. Guide plate 67 is mounted on the upper outer portion of punch holder 50 and retains the punch holder against rotation in its movement toward and from the stationary forming die. Operating rod 65 extends upwardly from projection 64 and slidably extends through openings in the top and bottom walls of supporting frame 10, as shown inFig. 1.

A switch operating block 68 is mounted on operating rod 65 between the upper and lower walls of frame 10 for alternately operating upper and lower electric control switches 69 and 70, respectively. Switch operating block 68 operates each switch into circuit closing position when engaged by the block. Each switch is normally operated to open position when block 68 disengages the operating arm on the switch. Switches 69 and 70 are of well known conventional construction and their structural details are, therefore, not illustrated.

Compressed air is the fluid preferably used for operating the draw press as herein shown and described. A suitable source of compressed air is supplied through pipe 71, see Fig. 4, through an air filter 72 and pressure regulator 73 to punch operating air supply tank 74. An air cushion reservoir or tank 75 is also supplied with air from pipe 71 through pressure regulator 76. Conventional types of air filters and pressure regulators well known in the art are used and are only diagrammatically illustrated in the diagrammatic view forming Fig. 4. The tanks are of conventional construction as are all of the valves used in controlling the air supply to different parts in operating the press.

Air cushion reservoir 75 has a pipe connection 77 to movable die cylinder 11 to supply compressed air to cylinder 11 above cylindrical piston 30 for normally moving piston 30 and movable die 44 downwardly toward stationary forming die 7. The air pressure in tank 75 is controlled by pressure regulator 76 so that the pressure is less than the pressure in tank 74. The capacity of cushion reservoir 75 is suflicient in comparison with that of cylinder 11 that the pressure in the cushion reservoir and cylinder 11 remains substantially constant regardless of the position of piston 30 in the cylinder. In operation of the press the compressed air in cushion reservoir 75 moves through pipe 77 to and from cylinder 11 without exhaust or loss of air except that which may escape by leakage. Air lost from leakage is replaced from the supply through pipe 71 and pressure regulator 76 to maintain substantially constant pressure in reservoir 75.

A main control valve 80 operated electro-magnetically is shown diagrammatically in Figs. 4 and and is controlled by a pair of manually operated electric switches 81 and 81. Valve 80 is of conventional form and so are switches 81 and 81'. Switch 81 is a two-way switch closing a contact in both the operated and release positions thereof for a purpose to be described. Switch 81 is a single switch closing a circuit in only the operated position. Valve 89 is preferably mounted on the rear wall of frame as diagrammatically indicated in Fig. 4, and switches 81 and 81' are preferably mounted at the front of the press on top 2 in a position convenient to the press operator, but not shown. The switches are provided so the operator is required to use both hands, one on each switch, during a cycle of operation of the press as a safety measure to prevent injury to the operator. The diagrammatic view in Fig. 5 illustrates how valve may be arranged to control air supply to operate the press. This valve 80 includes a stationary body 82, a slidable valve 83, an electro-magnet 84 for moving the valve into one position and a spring 85 for normally moving the valve into the position of rest when magnet 84 is not energized. Valve 83 is shown in the position of rest in Fig. 5.

A pipe 86 is connected to air supply tank 74 and conducts air to port 87 in valve 80. When electro-magnet 84 is energized, valve 83 is moved downwardly, as shown in Fig. 5, to a position where passage 88 in valve 83 connects port 87 to port 89, having pipe 90 extending from the valve to cylinder cap 19 for supplying compressed air above piston 20 to cylinder 15 for moving piston 20 downwardly and also for moving punch 58 downwardly to form a piece of sheet material. In this operation of valve 83, passage 91 therein is moved into position to register with ports 92 and 93 in the valve body. This establishes communication between pipe 94 connecting a port in cylinder base 16 with port 92 in valve body 82. .Pipe 95 connects port 93 with pipe fitting 55 for exhausting air from the lower portion of cylinder 15 in the downward movement of the punch piston through cooling chamber 54 in punch holder 50 for cooling the punch. The air is then exhausted from chamber 54 through exhaust opening 56 to the atmosphere. When the punch piston has rapidly moved downwardly to engage the punch with the sheet to be formed, the enlarged portion 22 on the piston rod engages in the cushion chamber 24 and the speed of movement is reduced and controlled by the adjustment of cushion adjusting screw 63 until the piston reaches the downward limit of move ment.

As the punchand punch piston are moved downwardly, the movable die will be moved downwardly by the pressure in cylinder 11 to engage the margin of the sheet and hold it against stationary forming die 7 with the desired pressure before the sheet material is engaged by the punch.

As soon as the downward movement of the punch is complete the operator releases switches 81 and 81 opening the circuit from source of current supply 96 through electro-magnet 84. Spring 85 returns valve 83 to the position of rest shown in Fig. 5. Compressed air from punch operating air supply tank 74 flowing through pipe 86 and port 87 of valve body 82 passes through passage 91 in valve 83 in registery with port 92 in body 82. Compressed air is supplied from port 92 through pipe 94 and the port in cylinder base 16 to cylinder 15 for moving piston 20 to the upper limit of movement. This upward movement will rapidly disengage the lower end of portion 22 from chamber 24 and packing gland 60. The upward movement of the piston picks up movable die holder 34 by engagement of boss 52 with Washer 53 so that the movable die is then moved upwardly with piston 34 against the pressure in cylinder 11 to the upper limit of movement shown in Fig. l. Passage 88 in valve 83 connects passage 89 and pipe 90 for exhausting air from the upper end of cylinder 15 to exhaust port 99, through exhaust pipe connected to muffler 101 and then to the atmosphere.

Valve body 82 has a passage 98 in the base portion connecting ports 93 and 99. Exhaust air therefore passes outwardly to the atmosphere through muifler 101 as well as through pipe 95 and punch holder 58.

As soon as the press operator releases switches 81 and 81', the circuit of switch 81 in the release position is closed through lower control switch 70 to electro-magnetic valve 104 for supplying energy from source 96 to operate valve 104. When the electro-magnet of valve 104 is energized compressed air will be supplied from the source through pipe 105 to pipe 109. Pipe 109 is connected to pipe fitting 4 9 on punch. holder 50. Compressed'air from pipe 109 passes through passage 26 and the bore in attaching screw 59 for ejecting the formed cap from 'punch 58 through the opening in lower stationary forming die 7 and passage 3 into base 1 and outwardly from the machine through an opening in base 1, not shown. This compressed air from valve 104,continues to flow through pipe 109 until upper die holder 34 and switch operating rod 65 have moved upwardly an amount suflficient to disengage switch operating block 68 from switch 70 so the switch contacts move to open position for opening the circuit to the electro-magnet for valve 104. When the circuit to valve 104 is open the valve cutsofl the air supply to pipe 109.

Further movement of switch operating rod 65 and switch operating block 68 engages block 68 with the arm of switch 69 to operate the switch to closed position. This closes the circuit from current supply 96 through switch 81 in release position and switch 69 to energize the electromagnet of valve 103. This opens valve 103 to supply compressed air from pipe 105 through valve 103 to nozzle 106 for ejecting the trimming formed during the drawing of the cap, outwardly from between lower forming die 7 and movable die 44 after it has moved apart. When piston 20 has moved punch 58 and movable die 44 with their connected parts to the upper position, shown in Fig. 1, switch operating block 68 will be moved upwardly an amount suflicient to disengage upper switch 69 and be positioned above said switch so both switches 69 and 70 will be in circuit opening position to cut oif air supply through valves 103 and 104. When switch operating block 68 is moved downwardly in drawing a sheet of plastic, switches 69 and 70 will be successively moved to circuit closing position. However, the circuit to valves 103 and 104 will be opened at switch 81 because the operator has to hold switch 81 in operated position during the entire time punch 58 is moved to its lower limit to form a sheet.

The machine operator is therefore required to put both hands on switches 81 and 81' after inserting a sheet to be formed into the press, and hold the switches during the entire downward movement of the punch and movable die'in engaging and forming the sheet material. The cushion chamber 24 and portion 22 of the piston rod cooperatewith cushion screw 63 to slow the speed of movement of the movable die upon engagement with the sheet to be formed and during the entire forming operation. As the punch and punch piston'reach the end of the downward movement and complete the forming of the sheet, the trimmer severs the formed portion of the sheet from the outer marginal portion. The operator then releases switches 81 and 81'. Main control valve 80 is then operated to cause the punch, punch piston and movable die to move upwardly away from the stationary die to the upper limit of movement of each. Switches 69 and 70 are operated to provide air under pressure to eject the formed part and the trimmed marginal portion through operation of valves 103 and 104 on the upward stroke.

The electric heaters 6 and 43 mounted in the grooves in lower die holder 4 and upper die holder 39 are connected to the source of current supply through wires 96 in series with suitable conventional controls, for maintaining the desired degree of heat in the upper and lower dies, as shown diagrammatically in Figure 4. This heats the portion of a plastic sheet to be drawn to soften it to the proper extent for efliciently performing the drawing or forming operation. This heating of a plastic sheet and the control of the speed of punch movement as it engages the sheet to be formed through the cushion chamher and cushion screw provides the desired timing of the press operation to secure etficient drawing of plastic sheet material.

8 "Air tanks 74 and 75 have conventional drainconnections with valves at the lower ends as indicated at 107. A' conventional form of lubricator 108 may be used in pipe.- 86 for supplying lubricant to the. punch piston: and cylinderin afrnanner well known in the. art; The, invention claimed is: i s i' f '1. A press of the class described comprising a support, a stationary forming die mounted on said support, a movable die cylinder mounted on said support having a piston therein carrying a movable die on one end mounted for reciprocating movement toward and from said stationary forming die, a punch cylinder mountedon said supporthaving a piston therein carrying a punch on one end mounted .for reciprocating movement toward and from said stationary forming die, fluid pressure containing means communicating with said movable. die cylinder for. normally moving the piston therein and said movable die towardisaid stationary'dietohold a piece to be formed engaged with said stationary die, a source of fluid under pressure, means connecting said source with said fluid pressure containing means for maintaining a substantially constant pressure therein less than the pressure of said source, manually operable means for controlling supply of fluid pressure from said source to said punch cylinder for moving said piston and punch toward said stationary die and also moving said piston and punch away from said die, and means operated in the movement of said punch away from said stationary die for operating the piston for said movable die to move said movable die and piston away from said stationary die against the fluid pressure in said movable die cylinder.

2. A press of the class described, comprising a support, a stationary forming die mounted on said support, a movable die cylinder mounted on said support having a piston movable therein carrying a movable die on one end mounted for reciprocating movement toward and from said stationary forming die, a punch, means mounting said punch for movement toward and from said stationary die in forming sheet material having a portion formed. to engage a portion of said movabletdie and attached piston for moving said movable die therewith 1 away from said stationary die'when said punch is moved away from said stationary die, fluid pressure means communicating with said movable'die cylinder for normally moving the piston therein and said movable die toward said stationary die to hold a piece to be formed engaged with said stationary die, and manually controlled operating means for moving said punch'toward said stationary die to form sheet material therein and for moving said punch, movable die and attached piston away from said stationary die against the fluid pressure in said movable die cylinder supplied by said fluid pressure means. i

3. A press of the character claimed in claim 1, wherein said movable die cylinder, piston and die are constructed and mounted in concentric relation to said punch cylinder, piston and punch. 4. A press of the character claimed in claim 2, where,- in said punch has a piston rod connection to said punch piston, said movable die cylinder is mounted. and formed in substantially concentric and coaxial relation about said punch piston rod, said movable die being of annular form aboutsaid punch and having a shoulder portion above said punch engaged by an upper portion of said punch for movement of said movable die away from said stationary die by said punch.

5. A press of the character claimed in claim 1, wherein a punch holder has a cylindr'ical'body formed with a chamber, a punch mounting extension on one end of said body, an extension on the opposite end receiving the lower end of said piston rod for mounting said punch holder thereon and providing a shoulder for engaging and moving said movable die member therewith away.

from said stationary die member, means for supplying cooling fluid to said chamberin said body, andmeans ac ion.

on said punch holder operating control means on the frame for controlling cooling fluid to said chamber.

6. A press of the character claimed in claim 1, wherein the stationary forming die has a lower die holder mounted on the top of said base formed on the upper face with an annular groove receiving heating means, and a lower die adapter is mounted on the upper face of said lower die holder to extend over, enclose said heating means and mount said stationary forming die on the upper surface thereof, and said annular movable die has an upper die holder formed with a plate portion attached to the lower end of the cylindrical portion on said cylindrical piston, said upper die holder having a plurality of downwardly extending arms on the periphery of said plate portion, an upper die holder plate mounted on the lower ends of said arms having an annular groove in the lower face receiving heating means, an upper die adapter mounted on the lower face of said upper die holder, enclosing the heating means in the groove in said upper die holder, and having said movable die mounted on the lower face thereof.

7. A fluid operated motor for presses comprising a movable die cylinder having a piston therein for reciprocating a movable die on one end thereof toward and from a stationary die, a punch cylinder having a piston therein for reciprocating a punch on one end toward and from said stationary die, fluid pressure containing means communicating with said movable die cylinder for normally moving the piston therein and said movable dietoward said stationary die to hold a piece to be formed engaged with said stationary die, a source of fluid under pressure, means connecting said source with said fluid pressure containing means for maintaining a substantially constant pressure therein less than the pressure of said source, manually operable means for controlling supply of fluid pressure from said source to said punch cylinder for moving said piston and punch toward said stationary die and also moving said piston and punch away from said die and means operated in the movement of said piston and punch away from said stationary die for operating the piston for said movable die to move said piston and die away from said stationary die against the fluid pressure in said movable die cylinder.

8. A fluid operated motor for presses of the class described comprising a movable die cylinder having a piston therein with a piston rod extending outwardly from one end of said cylinder, a punch cylinder having a piston therein with a piston rod extending from one end of said cylinder, said cylinders, pistons and piston rods being in substantially parallel relation with said piston rods extending outwardly from corresponding ends of said cylinders, fluid pressure containing means communicating with said movable die cylinder for normally moving the piston therein and its piston rod outwardly from said cylinder, a source of fluid under pressure, means connecting said source with said fluid pressure containing means for maintaining a substantially constant pressure therein less than the pressure of said source, manually operable means for controlling supply of fluid under pressure from said source to said punch cylinder for moving the piston and piston rod in said punch cylinder in opposite directions therein, means operated by said piston and piston rod in said punch cylinder for engagement with complementary means engaged with the piston rod of said movable die cylinder for moving said piston and piston rod in said movable die cylinder toward said cylinder against the pressure of said fluid pressure means.

9. A fluid operated motor of the character claimed in claim 8, wherein said movable die cylinder, piston and piston rod are formed and mounted in substantially concentric relation about said punch piston rod, and a shoulder portion is carried by said punch piston rod for engaging parts on said movable die piston rod for movement of said movable die piston rod and piston in said movable die cylinder in movement of said punch piston rod in one direction.

10. A fluid operated motor of the character claimed in claim 7, wherein a cushion chamber is formed in said punch cylinder and said punch piston has means engaging in said cushion chamber as said punch piston approaches one end of its movement in said punch cylinder for controlling and reducing the speed of said punch piston during further movement toward the end of the cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 2,490,625 Hall Dec. 6, 1949 2,521,388 Maynard et a1 Sept. 5, 1950 2,522,956 Middleton Sept. 19, 1950 2,640,325 Haller June 2, 1953 2,775,015 Erb Dec. 25, 1956 2,825,092 Hatch et al Mar. 4, 1958 OTHER REFERENCES Plastics Engineering Handbook (The Society of the Plastic Industry), published by Reinhold Publishing Corp., 1954, pp. 154-159. 

